A geophone is a known device that converts seismic energy (movement or displacement) to an electrical signal having a voltage that is proportional to the velocity of the seismic energy. They can be used, for example, to detect and quantify movement or displacement of the ground (earthquakes) or machine vibrations. They can also be used in oil exploration and mining, where a man-made seismic stimulus is applied to the earth, and a geophone is used to ‘read’ the reflection or response to the seismic stimulus, which may indicate the presence of oil or a specific mineral deposit (generally referred to as seismic surveying or prospecting).
U.S. Pat. No. 7,034,716, titled “Passive Real-Time Vehicle Classification System Utilizing Unattended Ground Sensors” describes one application of a geophone, for determining the type of a vehicle traversing terrain from acoustic and seismic noise emitted therefrom.
Although seismic energy is generally three-dimensional in nature, a geophone is typically configured to respond to single dimension. However, some applications require the full wave of seismic energy to be detected, and in such cases, a multi-component geophone can be used, where individual geophones are deployed for each dimension of interest. For instance, a three-axis geophone detects seismic energy in three mutually orthogonal dimensions: x, y and z directions.